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1.  Miter Saw "Clamping" Fixture:

When crown molding is cut per method 1 (Part 1 Crown on Horizontal Ceilings), it is helpful to hold the part securely to the saw table using an indexing or support fixture. Holding it by hand only will cause distortions and shifting of the part just when you don’t want it.

I have made a clamping fixture out of ¼ inch plywood and two thin strips of wood as shown below. My good old 10 inch Delta saw has holes drilled through the back of the fence that allowed me to fasten a sheet of plywood to increase the height of the fence. I used four ¼ inch flathead machine screws with wing-nuts for quick release. Once the full sheet was bolted in place, I used the saw to cut away some of the material to provide clearance for miter and bevel cuts. Then I glued on some sandpaper to provide friction.

The "clamp" part was also made out of one piece to start with. I glued a ¼ x ¼ inch piece of wood along the back so this raised edge would provide extra support. Two holes in the saw’s casting were plugged with some wooden dowel and clearance holes for ¼ inch bolts were drilled through. These bolts with wing-nuts hold the fixture in place. Note that the slots allow the units to be moved back or forth for different size molding. Once the whole piece was clamped in place, I used the saw to cut the piece in two and provide clearance slots for various miter settings. I also trimmed up a few corners.

To use the fixture, I rip some scrap pieces to fit each type of molding to be cut. They correspond to the imprint of the foot against the ceiling for Method 1. These 'gauge blocks' are positioned between the back fence and the fixture. The blocks are not shown in the photos. But I think you can see that the molding now has alignment at both sides of the saw. Note that the molding still rests on the saw bed, not on a piece of plastic (the one offered by a reputable warehouse). The two-part design provides a good reference and support on both sides of the blade. Keep in mind that this is not really a clamp but an indexing guide. The part still has to be held firmly in place while cutting. However, the sandpaper and "clamping" parts help to hold the crown in the correct position. On hindsight, I should have made the backboards longer. I have not provided any dimensions for this concept because every saw will have a different set of mounting holes. However, I believe these holes are present on all, or most, saws on the market.

2.  Marking and Cutting Gauges:

If you are planning to use Method 2 and cut more than a few pieces of molding, you might consider making the following simple fixtures. They help to identify how to orient the molding on the miter saw and to line up the cutting planes.  They are intended for 90° inside and outside corners only. To see how they are used go to Cutting Gauges.

3. Wall Angle Gauge:

In order to get a nice sharp edge with crown molding corners, it is helpful to know what the exact angle is between the two walls. One way is to use a square and judge the deviation from a right angle. A better way is to use a gauge with some means of reading the actual angle. Although tiny commercial units are available, I have made one using a six inch diameter protractor and some ¼ inch plywood. I didn’t think it wise to buy a unit with only a two inch diameter scale with divisions that are hardly readable.

For those of you who like to do some woodworking, I am providing the following ideas. You can adjust the size to your own liking. The unit consists of a base and arm that can swing around a bolt in the center of the protractor. The arm rotates over the base and closes into a compact unit six inches wide. The protractor is fastened to the narrower arm. On the base is a small piece of wood with a hairline scribed as shown. It is the reference line and is zero when both arms are closed. I notched the narrow arm to clear the reference block and also to clear the small bumps typically encountered with outside corners of two walls. The length of the arm and base is up to you. I choose 16 inches overall. The large protractor has divisions of one half degree which is better than most bevel settings on compound saws.

		Note that the unit can measure inside and outside angles from 0 to 360 degrees. Not only that, it can be used to measure vault angles and other intersections of walls and ceiling. I have also used it for layout work when cutting plywood sheets at various angles.

4. Nailing Blocks:

For wide molding you might consider adding support to the back side of the crown. Wooden blocks, 1.5 inches wide can be cut from a 2x4 (or 2x6 if necessary). First you need to measure dimension L of the crown molding. For standard 32/52 crown multiply this number by 0.85. This will be the width of the board you need. Rip the 2x4 or 2x6 to this width. Then using the miter or table saw, cut the blocks as shown. The angle corresponds to the spring angle of the crown. Note the dimension, L, should be just a bit less than the width of the crown face (say 1/32 inch). Knock off the sharp corner that would go up against the ceiling/wall intersection.